The invention concerns a swash plate pivoting bearing for a hydraulic axial piston machine in which rolling bearing segments are arranged between a hollow cylindrical bearing surface for the swash plate in a housing and a cylindrical bearing surface on the swash plate, which rolling bearing segments are retained in arc-shaped cages that are configured as solid cages and comprise a support peg for re-positioning the cage upon displacement from a desired position, said support peg extending parallel to the rolling element pockets and projecting beyond the cage width while being connected to a readjusting device.
In this known type of structure, a readjusting device associated to the swash plate pivoting bearing prevents the cage that receives the rolling bearing elements from slipping out of its predetermined region of movement, namely its favorable position in the pivoting bearing. In the absence of a readjusting device such slipping is possible because the rolling bearing elements not only execute rolling movements but also sliding movements due to rapid pivoting and/or vibrations and/or the mass inertia of the rolling bearing segment that lead to a positional displacement of the rolling element segment. This results in an unfavorable position of the retaining segment or segments relative to the direction of load.
Such swash plate pivoting bearings with different types of readjusting devices are described, for example, in DE-OS 28 26 928, DE-AS 25 21 312 or EP 01 82 354 B1. These readjusting devices require a point of articulation on the arc-shaped cage. From DE-GM 87 10 514, it is known in this connection to provide a bore in the cage and insert a metal pin into this bore which is then in contact with the readjusting device. A drawback of such arrangements is that in cage segments of small radial overall dimensions, this pin cannot be accommodated in the cage for lack of space.
The object of the invention is therefore to provide an improved cage of the pre-cited type in which, with the help of simple measures, the support peg can be arranged securely, reliably, and inexpensively on the cage, and the occurring restoring forces do not cause a wear of the cage.
The invention achieves this object by the fact that the cage and the support peg are made as a single piece out of a polymer material, and the support peg is surrounded, at least over a part of its axial length, by a metal ring.
By the configuration of the arc-shaped cage according to the invention it is assured that one-piece cages including the actual cage segment and the support peg can be produced without any problem in any desired size and dimensions. The metal ring connected to the support peg assures on the one hand that the cage segment has an adequate resistance to the contact pressure at its point of contact with the readjusting device and, on the other hand, that an adequate wear resistance to the sliding motion between the support peg and the readjusting device is created. Thus, the metal ring serves as a wear protector because, upon a direct contact of the support peg with the readjusting device, a considerable wear of the polymer material would take place at the point of contact. In addition, compared to the polymer material, the metal ring has a considerably higher permissible surface pressure.
Advantageous embodiments of the invention are described as follows. The metal ring is made of a steel material and subjected to a heat treatment. With this heat treatment, the steel material can be endowed with substantially higher strength values. The metal ring can comprise a projection on its inner peripheral surface and the metal ring can comprise a projection on its inner peripheral surface and the positive engagement thus formed creates an inseparable connection between the support peg and the metal ring. The metal ring may comprise a depression at least on a part of its periphery which radially inward oriented depression assures on the one side, as described above, that a positive connection is formed between the support peg and the metal ring, and on the other side, that the readjusting device can be reliably guided in the depression on the outer peripheral surface of the metal ring. Finally, the metal ring is sprayed over on its inner end face with cage material.
The invention will now be described more closely with reference to the following examples of embodiment.